Electric circuit breaker



April 8, 1941. D, PRINCE' 2,238,027

ELECTRIC CIRCUIT BREAKER Filed July 19, 1940 zr' Fig.1.

I a /7 9 2 as igz. 34 M M Inventor: David C. Prince,

Hrs Attorney.

Patented Apr. 8, 1941 ELECTRIC CIRCUIT BREAKER David 0. Prince, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application July 19, 1940, Serial No. 346,361

5 Claims.

My invention relates to electric circuit breakers, more particularly to those of the liquid blast type wherein arcing is extinguished by a blast of liquid such as oil caused in turn by are generated pressure.

The well-known oil-blast principle of arc interruption has been widely accepted in the circuit breaker field, chiefly because of the reliability and speed of circuit interruption made possible by correct application of the principle. At low or moderate voltages, the oil-blast circuit breaker can be operated many times without inspection or maintenance clue to the low rate of oil deterioration caused by arcing. For very high voltage circuits, such as 287 kv. for example, the oil blast design can also be used to advantage for both interrupting arcing and providing insulation against restriking of the arc provided the dielectric strength of the insulating oil is not permitted materially to decrease after repeated arc extinguishing operations.

Heretofore, it has been customary periodically to drain and filter the oil from oil blast circuit breakers, particularly those for high voltage circuits for the purpose of maintaining the oil at a high dielectric or insulating level. This is necessitated by the fact that a certain amount of carbonization of the oil takes place when the oil is subjected to-arcing. The precipitated carbon when mixed with the oil obviously decreases the dielectric strength to an extent depending upon the amount of carbon present. Repeated circuit interrupting operations may cause such turbulence in the oil body that the carbon is quite thoroughly mixed with the oil so that its dielectric strength is greatly decreased. When the breaker contacts are to be isolated in the open circuit position solely by the insulating liquid or oil, it will be apparent that carbonization presents a serious problem in high voltage installations.

In accordance with my invention, a high voltage circuit breaker of the oil blast type above referred to is provided with means for maintaining the oil at comparatively high dielectric strength in the region of the breaker contacts. To this end, the arc extinguishing oil blast is utilized to cause circulation of clean oil from a carbon separating chamber or reservoir to I the oil blast or pressure generating chamber of the breaker to replenish oil previously subjected to arcing so that the breaker contacts are insulated by oil having high dielectric strength.

The partially carbonized oil in the oil blast is expelled from the region of the contacts to recirculate to the carbon separating chamber.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view of high voltage electric circuit breaker structure to which the present invention is applied; Fig. 2 is an elevational view partly in section of the essential parts of the are interrupting unit shown in Fig. 1 and Fig. 3 is a sectional view taken along the line 3 -3 of Fig. 2.

The high voltage electric circuit breaker illustrated by way of example in Fig. 1 comprises an arc interrupting unit I formed by an insulating cylinder 2 of strong insulating material, and supporting insulators 3. The unit I terminates at one end in the mechanism housing 4 which is pivotally supported on one of the insulators at 5. The mechanism or linkage for opening and closing the breaker generally indicated at 4' is suitably connected to operating means (not shown) extending beneath the insulators by a rod 6' extending through the supporting insulator and tubular housing structure 6. The metallic housing 4 also constitutes one terminal of the interrupting unit I. The other terminal is indicated at 1 at the opposite end of the unit, this end of the unit having a sliding support indicated at 8 for coacting with the other insulator 3. In certain installations, a second similar interrupting unit is used as indicated. This arrangement is, however, optional and further description thereof is unnecessary for a complete understanding of the present invention.

Insofar as the general housing and supporting structure is concerned, further description thereof is believed to be unnecessary since it is of the same general type as that disclosed in my Patent 2,162,588, granted June 13, 1939, for Electric circuit breaker.

Referring more particularly to Fig. 2, the insulating cylinder 2 constituting the breaker casing is provided with an end closure member 9 constituting part of the terminal structure 1 for sealing within the casing a suitable arc extinguishing and insulating liquid Ill such as circuit breaker oil. Immersed in the oil are the relatively movable contacts, three sets of which connected in series are indicated at Il-l2, l3-l4 and I5|6. The contacts ll, I3 and I5 are mounted for reciprocal longitudinal movement with respect to the coacting fixed contacts which are in turn supported by an insulating baille structure l1.

Forthe purpose of operating the contacts ll, I3 and IS in unison, they are connected to a common insulating operating member indicated at l8 extending throughout the interrupting unit. As best illustrated by Fig. 3, the operating member l8 comprises a pair of parallel insulating rods which carry a yoke-like member IS on which the movable contact is resiliently supported as indicated at 20. Accordingly, when the operating member I8 is reciprocated by suitable operating means for controlling the circuit, the contacts H, I3 and I are simultaneously operated into or out of engagement with the corresponding fixed contacts l2, l4 and 16 respectively. The series connection through the breaker is completed by flexible conductors 2| and 22 interconnecting the fixed contact l2 and the movable contact [3, and the fixed contact l4 and the movable contact l5 respectively. The fixed contact I6 is connected to the terminal structure I by a flexible conductor 23. It will therefore be apparent that when the operating member I8 is moved toward the left, three breaks in series in the arrangement shown will be formed in the circuit.

The insulating bailie structure 11, referring more particularly to Fig. 3 forms a partition 30 dividing the interrupting cylinder 2 into a lower or pressure chamber 24, and an upper or pressure relief chamber 25. The lower chamber, which is completely filled with oil, is in turn subdivided into a pressure generating chamber 24' and an interrupting chamber 24". To this end, the insulating bailie I1 is provided with depending walls or bulkheads 26 and 21 which segregate the respective chambers except for apertures controlled by one-way valves 28 and 29 which are normally biased closed by a slight force and function in a manner hereinafter described.

The upper relief chamber, which is. preferably provided with an air space as indicated and vented through the housing 4 at is in communication with a chamber 30 at the end of the unit defined by the end wall 9 and the insulating bulkhead 21. The chamber 30 is in effect a reservoir and carbon separating or clarifying chamber, a sump 3| being formed at the lower part of the chamber where it is free of turbulence for the purpose of collecting carbon, sediment and other foreign matter that might affect the dielectric strength of the oil. It will be apparent that the carbon collecting means indicated at 3| is illustrated merely by way of example and that it is within the scope of my invention to employ any suitable carbon separating or collecting means in the chamber 30 for the purpose of clarifying and restoring the dielectric strength of the oil.

The operation of the circuit breaker is as follows: Let it now be assumed that the operating member l3 slidably mounted in the bulkheads 26 and 21 is moved toward the left to separate the series connected contacts I||2, l3-H and I 5-16. In the case of a high voltage power circuit, arcs will instantly form at each of these breaks. chamber 24', it will be observed, has but one possible way of relief, i. e., into the chamber 24" through the valve 28, the valve 29 being biased firmly closed by the arc pressure.

The arcs at the breaks l|-I2 and 13-14 on The arc pressure within the generating the other hand are located adjacent to and opposite interrupting ports 32 and 33 formed in the insulating baiiie IT communicating with the upper relief chamber 25. Accordingly, the pressure generated at the contacts l5-l6 is transmitted to the chamber 24" where it causes an arc interrupting blast of oil through each arc at the ports 32 and 33 respectively. Even after actual arc interruption the fiuid pressure still existing in the chamber 24' causes flushing of the oil from the chamber 24" so that carbonized oil is swept through the ports 32 and 33 into the exhaust chamber 25. This are interrupting operation is performed by a blast of clean oil of high dielectric strength and when the contacts remain in the open circuit position this oil effectively insulates the contacts at high voltage.

When the pressure generating arc is formed in the chamber 24', a certain amount of gas will be formed by the action of the are on the oil. Some of this gas may be expelled through the valve 28 into the chamber 24 where it eventually escapes through the ports 32 and 33. However, gas that is trapped in the chamber 24' must be vented in order to permit proper functioning of the breaker in future operations. To this end, a float valve 34 is provided in the bailie ll arranged normally to seal a port 34 in the upper wall of the pressure generating chamber. When, however, gas collects in the upper part of the chamber, the valve 34 drops to its unseated position, thereby permitting escape of the gas and refilling of the chamber 24' with insulating oil.

The refilling operation can take place only from the reservoir and clarifying chamber 33 since reverse fiow from the chamber 24" is prevented by the valve 28, the valve 23 on the other hand being adapted to open readily to permit refilling of the chamber 24' with clean oil from chamber 30.

With this arrangement, it will be apparent that the oil in the pressure generating chamber 24 is replenished, at least in part, after each interrupting operation so that the interrupting oil is completely recirculated to the clarifying chamber or reservoir 30 in accordance with operation of the breaker. The direction of recirculation of the oil in the exhaust chamber 25 is uniformly in the direction toward the clarifying chamber 33. There is therefore little likelihood of carbon deposition on the baflle structure IT.

The above described flushing action caused by the pressure generated in the chamber 24' interposes oil of high dielectric strength between the separated contacts. This in effect constitutes an insulating seal against restriking of the arc due to the recovery voltage and leaves the arc interrupting unit in suitable condition for an immediate second operation.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker of the oil blast type comprising an arc extinguishing and insulating liquid, relatively movable contacts separable to form a plurality of serially connected breaks in said liquid, means including a. pressure chamber for utilizing arcing pressure generated at one of said breaks so as to drive an extinguishing blast of liquid through the are at another of said breaks, a liquid collecting and clarifying chamber arranged to receive liquid used in said blast, one-way valve means for permitting flow of liquid from said clarifying to said pressure chamber, and means for directing the liquid blast after arc interruption to said clarifying chamber and for directing circulation of clarified liquid from said clarifying chamber of said pressure chamber and serially connected breaks.

2. An electric circuit breaker of the oil blast type comprising an arc extinguishing and insulating liquid, serially connected contacts separable to form a plurality of breaks in said liquid, means including a pressure chamber for utilizing arcing pressure generated at one of said breaks so as to drive an arc extinguishing blast of liquid through the are at another of said breaks, a liquid collecting and clarifying chamber arranged to receive liquid used in said blast, a one-way valve for permitting flow of liquid from said clarifying to said pressure chamber, and means including a second one-way valve for preventing reverse flow of blast liquid into said pressure chamber and for directing circulation of clarified liquid from said clarifying chamber to said pressure chamber and serially connected breaks.

3. An electric circuit breaker of the oil blast type comprising an arc extinguishing and insulating oil, serially connected contacts separable to form a plurality of breaks in said oil, insulating baflle structure forming a pressure generating chamber for utilizing pressure generated at one of said breaks so as to drive an arc extinguishing blast of oil through the arc at another of said breaks, a liquid collecting and clarifying chamber arranged to receive liquid used in said blast, a one-way valve controlling communication between said clarifying and pressure chambers, a second one-way valve controlling communication between said pressure chamber and the break subjected to said oil blast, and means including an exhaust chamber for directing the liquid blast after arc interruption to said clarifying chamber and for directing circulation of clarified liquid from said clarifying chamber by way of said valves to said serially connected breaks.

4. An electric circuit breaker of the oil blast type comprising insulating structure forming a pressure chamber, an insulating and arc extinguishing liquid filling said chamber, contacts separable to form a pressure generating break in said liquid, means for directing a liquid blast from said chamber for extinguishing arcing, a liquid clarifying chamber, means for directing flow of liquid used in said blast into said clarifying chamber and subsequently into said pressure chamber, and valve means in the upper wall of said pressure chamber arranged to be normally closed when said chamber is filled with liquid, said valve means being arranged to open when gas collects in the upper part of said chamber for venting said gas.

5. An electric circuit breaker of the oil blast type comprising a horizontally disposed insulating tubular casing, an insulating partition dividing said casing into upper and lower chambers, the lower chamber being in turn subdivided into a pressure generating chamber and a blast chamber, said upper chamber constituting an exhaust chamber that is in communication with said blast chamber through blast ports, insulating oil filling said lower chambers, an oil receiving and clarifying chamber arranged to receive oil from said exhaust chamber, a one-way valve for admitting oil from said clarifying chamber to said pressure generating chamber, a plurality of pairs of serially connected contacts disposed in said pressure generating and blast chambers respectively separable to form breaiks in said oil, gas venting means in the upper walls of said pressure generating chamber arranged to open only when gas collects in the upper part of said chamber, and additional valve means for directing uniform circulation of oil from said blast chamber to said clarifying chamber and subsequently to said pressure generating chamber in accordance with operation of said breaker.

DAVID C. PRINCE. 

